1. Field of the Invention
The present invention relates to a structure for coupling and fixing two chassis of a box shape, and more particularly, to a structure for stacking a chassis on another chassis in a building block system and coupling and fixing the chassis to each other.
2. Description of the Related Art
There was conventionally proposed a type of coupling and fixing structure of chassis of a box shape. Such a structure is disclosed in, for example, Japanese Laid-Open Patent Disclosure (JP-A-Hei3-103605). The coupling and fixing structure of a box shape of chassis will be described below with reference to FIGS. 1 to 3B.
Referring to FIG. 1, the chassis coupling and fixing structure includes two chassis 250A and 250B to be coupled. The chassis 250A and 250B are mainly constructed of front walls 261A and 261B, right side walls 262A and 262B, left side walls 263A and 263B, top plates 264A and 264B, bottom plates 265A and 265B, and rear walls 266A and 266B, respectively. Two convex portions 254A are provided at end portions of the top plate 264A of a chassis 250A in a horizontal direction on the side of the front wall 261A, respectively. Each of the convex portions 254A is of a rectangular block manner. The chassis 250B has two concave portions 253B provided on end portions of the bottom plate 265B of the chassis 250B in a horizontal direction on the side of the front wall 261B in correspondence to the convex portions 254A. Each of the convex portions 254A has a hole 256A penetrating from the front side to the rear side and each of the concave portions 253A has a tapped hole 256A on a position corresponding to the hole 256A. Screws 255 couple the chassis 250A and 250B to each other. Additionally, the chassis 250A has two tapped holes 257A provided within the chassis 250A in the end portion of the top plate 264A in the horizontal direction on the rear wall 266A side and the chassis 250B has two holes corresponding to the holes 257A and provided within the chassis 250B on the end portions of the bottom plate 265B in the horizontal direction o the rear wall 266b side.
More particularly, referring to FIG. 2, the convex portion 254A provided at a corner of the left side wall 263A and the front wall 261A on the top plate 264A of the chassis 250A has a top plate 274A parallel to the top plate 264A of the chassis 250A, a first side wall 273A straightly extending from the side wall 263A of the chassis 250A, and a front wall 271A straightly extending from the front wall 261A of the chassis 250A. A rear wall 276A of the convex portion 254A extends vertically and upward from the top plate 264A of the chassis 250A. A second side wall 272A of the convex portion 254A extends vertically and downward from the top plate 274A and is bent in a direction of the first side wall 273A on the way and further extends vertically and downward to the top plate 264A again. The bent portion 258A is inclined upward in a direction from the front wall 271A to the rear wall 276A. The convex portion has a hole 256A penetrating from the front wall 271A to the rear wall 276A. Such convex portions 254A are provided at corners between the right side wall 262A and the front wall 261A and between the left side wall 263A and the front wall 262A on the top plate 264A of the chassis 250A.
The concave portion 253B provided at a corner between the front wall 261B and the left side wall 263B on the bottom plate 265B of the chassis 250B has a structure fitting to the above mentioned convex portion 254A. The concave portion 253B has an upper plate 274B and a rear wall 276B extending from the bottom plate 262B to the upper plate 274B. The concave portion 253B further has a side wall 272B extending vertically and upward from the bottom plate 265B and is bent in a direction opposite to the left side wall 262B and further extending vertically and upward to the top plate 274B again. The bent portion 258B is inclined upward in a direction from the front wall 261B to the rear wall 276B. A tapped hole 256B is provided on the rear wall 276B. The concave portion 253B provided at a corner between the front wall 261B and the right side wall 262B on the bottom plate 265B of the chassis 250B has a symmetric structure to the above mentioned concave portion.
Next, a method of coupling the chassis 151 and 152 will be described below.
The chassis 250B is first placed on the top plate 264A of the chassis 250A on a position displaced from the front wall 262A in the direction of the rear wall 264A. Then the chassis 152 is moved in a direction of the front wall 261A until the inclined bend portions 258B of the concave portions 253B fit to the corresponding inclined bent portions 258A of the convex portions 254A. After the convex portions 254A and the concave portions 253B are mated, the chassis 250A and the chassis 250B are coupled to each other by screws 255 passing through the holes 256A to the tapped holes 256B. Thereafter, a user goes to the rear side of the chassis 250A and 250B and fixes between the chassis 250A and 250B with screws 259 there, as shown in FIGS. 3A and 3B.
In the conventional chassis coupling and fixing structure described above, the chassis 250B needs to be moved in the direction of the front wall 261A of the chassis 250A. However, there is no guide on the top plate 264A of the chassis 250A and, therefore, there is a problem in that it is difficult to position the chassis 250B such that the concave portions 253b mates the convex portions 254A.
Moreover, in the conventional chassis coupling and fixing structure, there is another problem in that after the chassis 250A and 250B are coupled to each other with the screws 255 on the front wall 262A side, a person must go to the rear wall 266A side to fix the chassis 250A and 250B with the screws 259, resulting in worse workability.
Further, there is still another problem in that because the screws 259 need to screwed within the chassis on the rear wall side, a space for constituent elements to be mounted becomes small.